NCERT Solutions for Class 9 Chemistry: Is matter around us pure

Class 9 is the first stepping stone for a student in the competitive world. With the introduction of the CBSE Board Exam for class 10 a few years back, this has become an important gateway for a student. Based on the results of class 9th a student selects his future stream of Science, Commerce or Arts suiting his interest.

Takshila Learning is providing NCERT Solutions for Class 9 Chemistry as per the latest syllabus by CBSE. Class 9 is the building block for the CBSE Class 10 Board Exams, not only for your exams but also for your higher studies and career. Chemistry is the most essential subject and the knowledge in this field opens up wider career opportunities for the students.

Below you can find the NCERT solution for Class 9th Chemistry. You can get a Solution for the all-important question of “Matter in Our Surroundings“

Intext questions (set 1)

Page no. 15

 

Ques 1: What is meant by a substance?

Answer: A material that are composed of only one type of particles is called pure substance. All the constituent particles of a pure substance Have same chemical nature Aerial dad is composed of only one type of particles is called pure substance. All the constituent particles of a pure substance Have same chemical nature

 

Ques 2:  List the points of differences between homogeneous and heterogeneous mixtures.

Answer:

Homogenous mixture	Heterogenous Mixture
Homo genius mixtures have uniform composition	Heterogeneous mixtures have a non-uniform composition
It has no visible boundaries of separation between its constituents.	It has visible boundaries of separation between its constituents.

 

 

Intext questions (set 2)

Page no. 18

 

Ques 1:  Differentiate between homogenous and heterogeneous mixtures with examples.

Answer: Homogenous mixture is a mixture having a uniform composition throughout the mixture. For example, mixture of salt in water, sugar and water, copper sulphate in water, iodine and alcohol, alloy, and air have uniform composition throughout the mixtures.

 

On the other hand, I Heterogenous mixture is a mixture having a non-uniform composition throughout the mixture. For example, composition of mixtures of NaCl and Iron feelings, salt and sulphur, oil and water, chalk powder in water, wheat flour and water, milk and water are not uniform throughout the mixtures.

 

Ques 2: How are sol, solution and suspension different from each other?

Answer:

Sol	Solution	Suspension
They are heterogenous in nature.	They are homogenous in nature.	They are heterogenous in nature.
They scatter a beam of light and hence show Tyndall effect.	They do not scatter a beam of light and hence do not show Tyndall effect.	They scatter a beam of light and hence show Tyndall effect.
They are quite stable	Examples of solution are : salt in water, sugar in water.	Examples of suspension are: sand in water, dusty air.

 

 

Ques 3: To make a saturated solution, 36g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.

Answer: Mass of solute (NaCl) = 36 g

Mass of solvent (H₂O) = 100 g

Mass of solution (NaCl + H₂O) = 136 g

Concentration = Mass of solute/Mass of solution x 100

Concentration = 36/136 x 100 = 26.47%

Hence, the concentration of the solution is 26.47%

 

 

Intext questions (set 3)

Page no. 24

 

 

 

Ques 1: How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25°C), which are miscible with each other?

Answer: Kerosene and petrol are miscible liquids also the difference between their boiling point is more than 25°C so they can be separated by the method of distillation .

 

In this method, the mixture of kerosene and petrol is taken in a distillation flask with a thermometer fitted in it. We also need a beaker , a water condenser and a Bunsen burner. The apparatus is arranged as shown in the above figure. Then, the mixture is heated slowly. The thermometer should be watched simultaneously. kerosene will vaporize and condense in the water condenser. The condensed kerosene is collected from the condenser outlet, whereas petrol is left behind in the distillation flask.

 

Ques 2:  Name the techniques used to separate the following:

(a)Butter from curd.

• By centrifugation

(b) Salt from seawater

• By evaporation

(c) Camphor from salt.

• By sublimation

 

Ques 3: What type of mixtures are separated by the technique of crystallization?

Answer: The crystallization method is use to purify the solids.

 

Intext questions (set 4)

Page no. 24

 

 

Ques 1: Classify the following as physical or chemical changes:

• Cutting of trees
• physical changes
• Melting of butter in a pan
• Physical changes
• Rusting of almirah
• Chemical changes
• Boiling of water to form steam
• Physical changes
• Passing of electric current through water and water breaking into hydrogen and oxygen gases.
• Chemical changes
• Dissolving common salt in water
• Physical changes
• Making a fruit salad with raw fruits.
• Physical changes
• Burning of paper and wood
• Chemical changes

 

Ques 2: Try segregating the things around you as pure substances and mixture

Answer: Listed below are the classifications based on pure substances and mixtures:

Pure substance	Mixtures
Water	Soil
Salt	Salad
Iron	Air
Diamond	Steel

 

Exercises:

Page no. 28

 

 

 

1. Which separation techniques will you apply for the separation of the following?

(a) Sodium chloride from its solution in water.

• Evaporation

(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.

• Sublimation

(c) Small pieces of metal in the engine oil of a car.

• Filtration or centrifugation or decantation

(d) Different pigments from an extract of flower petals.

• Chromatography

(e) Butter from curd.

• Centrifugation

(f) Oil from water.

• Using separating Funnel

(g) Tea leaves from tea.

• Filtration

(h) Iron pins from sand.

• Magnetic separation

(i)Wheat grains from husk.

• Winnowing

(j) Fine mud particles suspended in water.

• Centrifugation

 

2. Write the steps you would use for making tea. Use the words solution, solvent, solute, dissolve, soluble, insoluble, filtrate, and residue.

Answer: First, water is taken  as a solvent in a saucer pan. This water is allowed to boil. During heating, milk and tea leaves are added to the solvent and salute. The former solution. Then, the solution is poured through a strainer. The insoluble part of the solution remains on the screen hour as the residue. Sugar added to the filtrate, which dissolves in the filtrate. The resulting solution is the required tea

 

3. Pragya tested the solubility of three different substances at different temperatures and collected the data as given below (results are given in the following table, as grams of a substance dissolved in 100 grams of water to form a saturated solution).

Substance dissolved	Temperature in K
	283	293	313	333	353
	Solubility
Potassium nitrate	21	32	62	106	167
Sodium chloride	36	36	36	37	37
Potassium chloride	35	35	40	46	54
Ammonium chloride	24	37	41	55	66

(a) What mass of potassium nitrate would be needed to produce a saturated solution of 

potassium nitrate in 50 grams of water at 313K?

 (b) Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the 

solution to cool at room temperature. What would she observe as the solution cools? Explain.

(c) Find the solubility of each salt at 293 K. Which salt has the highest solubility at this 

temperature?

(d) What is the effect of change of temperature on the solubility of a salt?

Answer: (a) Since 62 g of potassium nitrate is dissolved in 100g of water to prepare a saturated solution of 313 K, 31 g of potassium nitrate should be in 50 g of water to prepare a saturated solution at 313K.

 

(b) amount of potassium chloride that should be dissolved in a saturated solution increases with temperature. Does, as the solution cools some of the potassium chloride will precipitate out of the solution.

 

(c)The solubility of the souls at 293K are :

Potassium nitrate-32g

NaCl – 36g

Potassium chloride-35 g

Ammonium chloride – 37g

 

Ammonium chloride has the highest solubility at 293K.

 

(d)The solubility of salt increases with temperature.

 

4. Explain the following giving examples.

(a) Saturated solution

(b) Pure substance

(c) Colloid

(d) suspension

Answer: (a) Solution in Which no more salute can be dissolved at a particular temperature is known as saturated solution. For example, if the aqueous solution of sugar no more sugar can be dissolved at room temperature.

 

(b) A pure substance consisting of a single type of particle, all constituent particles of the substance have the same chemical properties. For example, water, sugar, salt etc.

 

(c) A colloid is a heterogeneous mixture whose particles are not as small as solution, but they are so small that cannot be seen by naked eye. When a beam of light is passed through a colloidal then the part of the light becomes visible. For example, make, smoke etc.

 

(d) A suspension is a heterogeneous mixture in which solids are disposed in liquids. The salute particles in suspension do not dissolve but remain suspended throughout the medium. For example, pains, muddy water Chalk water mixture is etc.

 

5. Classify each of the following as a homogeneous or heterogeneous mixture.

soda water, wood, air, soil, vinegar, filtered tea.

Answer: Homogeneous mixtures: soda water, air, vinegar, filtered tea

Heterogeneous mixture: wood, soil

Note: pure air is homogeneous mixtures, but polluted air is heterogeneous mixture.

 

6. How would you confirm that a colourless liquid given to you is pure water?

Answer: Take a sample of colourless liquid and put on stop if it starts boiling exact at 100c then it is pure water. Any other colourless liquid such as vinegar always have different boiling point. Also observe carefully that after sometimes whole liquid will convert into vapour without leaving any residue.

 

7. Which of the following materials fall into the category of “pure substance”? 

(a)Ice

(b)Milk

(c)Iron

(d)Hydrochloric acid

(e)Calcium oxide

(f)Mercury

(g)Brick

(e)Wood

(f)Air.

Answer: The following materials fall in the category of a “pure substance”:

(a)Ice

(c)Iron

(d)HCL

(e)Calcium oxide

(f)Mercury

 

 

8. Identify the solutions among the following mixtures.

(a) Soil

(b) Sea water

(c) Air

(d) Coal

(e) Soda water

Answer: The following mixtures are solutions:

(b)sea water

(c)Air

(e)Soda water

 

 

 

9. Which of the following will show the “Tyndall effect”?

(a) Salt solution

(b) Milk

(c) Copper sulphate solution

(d) Starch solution.

Answer: Tyndall effect is shown by colloidal solution. Here milk and starch solution are colloids there for milk and starch solution will show Tyndall effect.

 

10. Classify the following into elements, compounds and mixtures.

(a) Sodium

(b) Soil

(c) Sugar solution

(d) Silver

(e) Calcium carbonate

(f) Tin

(g) Silicon

(h) Coal

(i)  Air

(j)  Soap

(k) Methane

(l) Carbon dioxide

(m) Blood.

Answer:

Elements: sodium, tin and silicon.

Compounds: calcium carbonate, methane and carbon dioxide.

Mixtures: soil, sugar, coal, Air, soap and blood.

 

 

11. Which of the following are chemical changes?

(a) Growth of a plant

(b) Rusting of Iron

(c) Mixing of iron filings and sand

(d) cooking of food

(e) digestion of food

(f) Freezing of water

(g) Burning of a candle

Answer: The following changes are chemical changes:

(a)Growth of a plant

(b) Rusting of iron

(d) cooking of food

(e) Digestion of food

(g) Burning of a candle.